The daily cruise newsletter, showing all planned events for each day, is published in English, French, Spanish, Italian, and maybe Portuguese (I forget); at least one TV channel is in Spanish; and one crew member is assigned to assist people who don't speak English. However, such people would find the cruise a struggle.
The dining room menu is in English only and no care is taken to provide diners with a waiter speaking their language (although the crew is multi-national). Ship announcements are in English only.
Ana's first language is Spanish, but of course she had to spend most of the holiday speaking English. She coped well even with the wide variety of accents we encountered.